Small marine vessels and the like are provided with radar reflectors for preventing maritime disaster, and particularly, in congested sea areas, nighttime navigation, under poor weather conditions such as fog and so forth, it is the duty of such marine vessels to sail with radar reflectors mounted.
Conventionally, a so-called all-directional corner reflector capable of catching radar waves from all directions is used, such being comprised of eight triangular corner reflectors, each of these comprising three sides of metal plates which are perpendicular to one another.
However, since such an all-directional corner reflector is formed in such a manner that the three sides of metal plates are constructed as one body, the corner reflector is stored in such a state that the three sides of metal plates remain perpendicular to one another, that is to say, in a three-dimensional state.
As a result, the entire shape of the reflector is so bulky that a greater storage space is required, and also, care must be taken so as not to deform the three sides of the metal plates by bumping them against surrounding objects or by allowing them to be pressed by surrounding objects. In response to this problem, a foldable radar reflector has been developed. (See Japanese Unexamined Utility Model Publication No. 62-80412.)
The aforementioned all-directional corner reflector has limits regarding the angles of incidence and reflection of radar waves, as it can be understood from the shape thereof. With respect to an isosceles triangle corner reflector, it has approximately the same angle of reflection in both the horizontal and longitudinal directions.
Accordingly, the greatest angle of reflection at the width of approximately 40.degree. (-3 dB half-voltage value) is 36.degree. upwards when the triangle serving as the base (bottom reflector plate) is placed flat. (See a technical reference entitled "EFFICIENCY OF RADAR REFLECTOR FILLED WITH HELIUM GAS" issued by Tokimec Engineering Inc. dated May 21, 1996.) Therefore, when the reflector is installed, it is necessary to place the bottom reflector plate at an angle of 36.degree. upward. Incidentally, this upward angle is referred to as a "detection design angle".
However, with respect to the radar reflector according to the conventional example, a string is passed through holes formed in the main reflector plates, and the radar reflector is suspended by attaching the string to a predetermined location. Accordingly, in the event that the radar reflector is subjected to an external force such as the wind, the reflector is swayed at random in up and down directions, forward and backward directions, right and left directions, and so on, so that it is difficult to maintain the bottom reflector plate at the detection design angle. Consequently, it is difficult to catch and reflect radar waves effectively over a wide area.
The object of the present invention is enabling to assemble and install such an all-directional corner reflector at the detection design angle in a precise and yet easy manner.
Another object of the present invention is to provide an all-directional corner reflector which is not bulky for storage.
The other object of the present invention is enabling to surely assemble an all-directional corner reflector from the stored state even in case of emergency.